JPH0364716A - Projection lens for projection television - Google Patents

Abstract

PURPOSE:To compensate chromatic aberrations while maintaining a large aperture ratio and to obtain a large view angle and superior image forming performance by using a plastic lens which is made aspherical and constituting a lens which has large refracting power as a glass lens, and satisfying specific conditions. CONSTITUTION:A 1st group lens G1, a 3rd lens G3, a 4th group lens G4, and a 5th group lens G5 are composed of glass lenses and a 2nd group lens G2 and a 6th group lens G6 are composed of plastic lenses. The conditions shown by inequalities are satisfied. Here, psi1.2 is the composite power of the 1st and 2nd group lenses, psi4.5 the composite power of the 4th and 5th group lenses, psi3 the power of the 3rd group lens, psi6 the power of the 6th group lens, psi2 the power of the 2nd group lens (the power of the whole system is 1), and psi3 the Abbe number of the 3rd group lens. Consequently, the chromatic aberrations are compensated and the superior image forming performance with the large view angle and a sufficient quantity of marginal light is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a projection lens used in projectors, :f, action televisions, and the like.

[Conventional technology]

Projection TVs project images from a CRT projection tube in three colors (red, green, and blue) onto a screen using three projection lenses to display a large color image. Considering the thinning and downsizing of such projection televisions, etc., the projection lens used is required to have a large angle of view, a large aperture ratio, and good imaging performance.

Conventionally, the above-mentioned projection lenses used only glass lenses to maintain quality through high processing precision, or only plastic lenses to reduce costs and obtain a large aperture ratio. Many systems have been proposed, including hybrid systems that use glass lenses and aspherical plastic lenses.

[Problem to be solved by the invention]

However, in a conventional projection lens made of a glass lens, there are problems in that improving the imaging performance while maintaining a large aperture ratio increases the size and cost, and sharply deteriorates the peripheral performance. Furthermore, although a projection lens constructed entirely of plastic lenses using aspherical surfaces is suitable for large apertures, the processing accuracy cannot be expected to be as high as that of a glass lens, so there is a problem in that the designed performance cannot be fully demonstrated. Furthermore, plastic lenses have a problem in that their refractive index and shape change due to temperature fluctuations, which changes the focal position and deteriorates imaging performance.

In addition, in projection televisions, it is said that there is no need to achromatize each lens that projects the three colors of red, green, and blue separately from the projection tube.
When measuring the spectrum of each actual projection tube, a wide emission spectrum was observed for blue, and a wide emission spectrum was observed for green and red.
In this case, a spurious emission spectrum is observed. Therefore, in a projection lens that is not achromatic, the imaging performance for each color is degraded, which poses a problem in improving color reproducibility.

[Means to solve the problem]

In order to solve the above-mentioned problems and obtain a projection lens with a large angle of view and excellent imaging performance while maintaining a large aperture ratio, the control lens for a PROJIEXIGON television according to the present invention was constructed as follows.

In order from the screen side, the first group lens is a positive lens, the second group lens is a meniscus-shaped positive lens, and the third group lens is a CR lens.
Consists of a negative lens with a more strongly concave surface facing the T side, the 4th group lens is a positive lens with convex surfaces on both sides, the 5th group lens is a positive meniscus lens, and the 6th group lens is a negative lens with a concave surface facing the screen side. A projection lens for a projection television consisting of six elements, in which the second group lens and the sixth group lens are each plastic lenses having at least one aspherical surface, and the following conditions (a) to (e) are met. A projection lens for a projection television, which satisfies the following.

(a) 0.5<ψ+, z<1.1 (b) 1.1<
ψ4. S<1.4 (C) 0.55<|ψ3|<0.9, ν, <40 (d) 0.9<lψ61<1.1(e) 0
<ψ2<0.4 However, ψ1□: Bottom power ψ4 of the first group lens and the second group lens. ．． ; Combined power of the 4th group lens and 5th group lens ψ3 : Power of the 3rd group lens ψb : Power of the 6th group lens ψ2 : Power of the 2nd group lens (However, the power of the entire system is assumed to be 1.) ν, :3rd
Atsbe number of group lens [effect] By using aspherical plastic lenses, good aberration performance is ensured, and by configuring lenses with large refractive power as glass lenses,
Changes in optical performance due to temperature changes are suppressed to a non-problematic level, and all plastic lenses are thin and have a meniscus shape for ease of molding.

Condition (a) relates to the combined power of the first group lens and the second group lens, and if the upper limit is exceeded, it becomes difficult to correct the special G sagittal flare, making it impossible to achieve a wide angle of view. Moreover, if the lower limit is exceeded, the total length of the I-men's type will become longer, and the structure of the projection television will become larger, which will cause an increase in cost.

Furthermore, if this lower limit is exceeded and the total length of the one-nons system is not changed, the power of the fourth lens group and the fifth R lens will be increased, making it impossible to balance on-axis and off-axis aberrations.

Condition (t)) relates to the combined power of the fourth group lens and the first group lens, and if the upper limit is exceeded, it becomes difficult to correct spherical aberration, making it impossible to realize a large aperture ratio.

Furthermore, if the lower limit is exceeded, it becomes difficult to correct coma aberration, making it impossible to achieve a wide angle of view.

Condition (C) is to balance chromatic aberration correction with other aberration corrections, and if the power ψ3 of the third group lens exceeds the upper limit, it will be difficult to correct spherical aberration, making it impossible to achieve a large aperture. . Furthermore, if the lower limit is exceeded, chromatic aberration correction becomes insufficient.

Furthermore, when the number ν3 exceeds the range, especially the first, fourth, and fifth groups are positive! The Atsube number is 60 as 2.
If a normal glass lens of about 100 mL is used, the balance between these lenses will not be maintained, and chromatic aberration correction will not be able to be performed satisfactorily.

Condition (d) is for flattening the image plane; if the upper limit is exceeded, the curvature of field will be over-corrected, and if the lower limit is exceeded, the curvature of field will be under-corrected.

〔Example〕

Hereinafter, FIGS. 1, 3, and 5 are cross-sectional views of each of the projection lenses of Examples 1 to 3.

In each embodiment, the second group lens Gl, the third group lens G
3. The fourth group lens G4 and the first group lens Gs are glass lenses, and the second group lens G2 and the sixth group lens G6 are plastic lenses.

In each example, the 13th surface is the glass T of the projection tube surface.
The 14th surface is its phosphor screen, and a liquid or gel-like filler M is filled between the projection tube surface glass T and the first group lens G to prevent an increase in contrast due to surface reflection. ing.

In the following description, rl+rZt...+r14 is the paraxial radius of curvature of each surface of the lens and projection tube surface glass, d.
, d. ...tdlff is the distance between each surface, N□.

N4,..., No, is the refractive index for the d-line, ν□
, ν4,,..., ν. , is the Abbe number for the d-line.

Also, the shape of the aspherical surface is X, Y, with the optical axis direction as the Z axis, similar to a general aspherical lens. In the rectangular coordinates of Z, the approximate radius of curvature of the vertex is r, the conic constant is k, and the higher-order aspheric coefficients are A-, A6, As, and A+.

When H-π71 wisdom It is a rotationally symmetric aspheric surface represented by .

In addition, the unit of the radius of curvature and the length of the gap in the following numerical data is "ko".

(Example 1) Focal length: 82.577mm, Magnification: 0.09610
Diameter ratio -1:0.99 ψ1□-0.70, ψ. ,, = 122ψ3−−
0.64,ψ, =-1.19ψ. = 0.19 r, = 92.93 d+ = 16.25 Na+ = 1.639 c. ．．
=-t. 23r z-815.72 dO1.00 Nd2-1.000r3=63.4
3 d,-6,oo Nd3=1.492 ci,3=6
1.3r. = 87.86 d4= 6.54 Nd4=1.000rs-409
．． 75 d-, = 4.00 Nas=1.728 νa
s=28.3r6 = 76, 16 d. =13.17 N,h=1.000r, -
89.42 at =20.50N. tt=1.589 ν.
i'y=61.395.11 =11.88 211.89 = 8.50 83.90 +o=31.12 -30.66 , := 3.20 N, .

-35,50 1□-5,00 0 ,,=10.30 ■ r3: Aspherical surface : o, ooo.

: -0,1165X10-5 : 0.1537 X 10-” : −0,2964X10−” : 0.9118XIO-” r: Aspherical surface N=o=1.0OO N, 9=1.517 N1゜ Nd,z Nd, 3 r　8　: 11 rq= 9 r　　　　+o= r lI= r　　　　　+z= r　　13= r　、、＝ =1.000 =1.491 =1.438 =1.542 C9=64.2 ν4□=58.2 ν□, =63.8 ν□, =55.5 r4: Aspherical surface o, ooo.

0, 1885 x 10-' 0, 1777 x 10-' 0, 2939 x 10-' 0.9841
: -0,3192X10-8As : 0
．． 1860xlO-”A,.: -0,7189
xlO-" (Example 2) Focal length -82,429 mm, Aperture ratio = 1:0.99 ψ,, = 0.57, N4,5 ψ, = -0,58, ψb ψ, = 0.30 r l = L12.87 ct, = 9.74 r z = 297.30 dz = 7.33 r, = 63.75 d3 = 8.02 r4 = 114.42 da = 6.83 r s = 246.97 N,,=1.638 Ndz=1.oo.

Na4=1.00O Naz=1.492 -0.5000 o, ooo.

o, ooo.

o, ooo.

o, ooo.

Magnification = -0,0961 = 1.25 = -1,23 ・ν□ = 55.5 Stain 3 = 61.3 d, = 3.00 rb = 72.66 di, = 9.73 rt = 83.66 dy = 17.76 r8 = -117,84 ds -17,07 r, = -775,71 d, = 9.14 rl. = -86,44 dl. -32,84 r,,=-29,94 dll-3,20 r1□-~35.50 d,□=5.0O r,,=OO N,,=1.728 N,,=1.0OO Ndv=1.589 Nds=1.00O N,,=1.517 N□. =1.00O N□, =1.491 N1□ =1.438 shi, 5=28.3 shay=61.3 shi9=64.2 νd11 =58.2 νddl −63,8 d+z=10. 30 Nap3=1.542
C413r, 4: C0 r,: Aspherical surface r4: Aspherical surface k: 0,0000 0.0000
=55.5 A, : -0,9811xlO-6Ah
: 0.6449xlO-'A, :
-0,2587X10-th A1゜: 0.86
15xlO 5r: Aspherical k neat, ooo.

A4: -0,1711X10-'A,
: -0,2031X10-'As : 0.
1448xlO-”A1゜: -0,7534X1
0 pull 5 (Example 3) Focal length = 82.433 mm, Aperture ratio = 1:0.99 ψh2 = 0.80, N4.5 ψ, = -0.79, N6 ψ, = 0.29 r+ = 86 .07 di = 17.01 rz = 547.76 dZ = 2.31 Nd+ = 1.639 Nd□ = 1.000 0, 1696 x 10-6 -0.7440 x 10-'.

-0,1793X10-” 0.7065X10-1S r, 2: Aspherical surface -0,5000 o, ooo.

o, ooo.

o, ooo.

o, ooo.

Magnification -0,0961 = 1.25 = -1,23 ν□=55.5 r, = 62.26 (L+-8,24 r, -106,70 d4 = 4.13 "5 = 302.46 d, -3゜0O r= = 60.51 d, =12゜64 rt-87,21 d7=19.03 r, = -91,57 dl =11.65 r, -134,10 d, - 8゜97 r, o= -67,43 d+o=30.77 r + + = -29,94 d, -3゜20 r +z= -35,50 dtx=5.0O N, l:l-1, 492 Naa""1.00O N, 5 = 1.728 Nai = 1.0OO Ndt = 1.589 Nag - 1,00O N,, = 1.517 Naro = 1.0OO N□, -1,491 N0Z = 1.438 Shi, i, =61.3 Shio-28.3 Shi?-61.3 Shi,, -64.2 Shiro.-58,2 ν□2 =63°8 rt3-clt:l d+z= 10.30 Nd+i = 1.542
νd, 1=55.51", 4== oO r,: Aspherical surface r4: Aspherical surface k: 0.0000 0.0000
A= knee 0.1105x10-50.2228x
lO-hA6: 0.6642X10”90.206
1X10-9Ae: -0,2522X10-
” -0,1937X10~ ■AIO: 0.8
587X10-"0.7969X10-"r,:
Aspherical surface r, 2: Aspherical surface k knee i, oooo -0,5000
A: 0.8443X10-” 0.
0000A, : -0,2849xlO-"
0.0000A, +8 0.1602X1
0-" 0.0000A, ): -0゜9
741
6 is filled with ItM to prevent a decrease in contrast due to surface reflection and a rise in temperature on the surface of the projection tube, but this is not essential. The surface (12th surface) is made substantially flat, and the 6th group lens G
It is also possible to use air as the medium between the projection tube 6 and the projection tube surface glass T.

FIG. 2, FIG. 4, and FIG. 6 are aberration curve diagrams of each projection lens of Example 1 and Example 3. As can be seen from the aberration curves of these examples, Television projection lenses maintain a large aperture ratio with an F-number of 0.99 while correcting chromatic aberration, achieving excellent imaging performance at a wide angle of view.

can be reduced.

[Brief explanation of drawings]

Figure 1 is a sectional view of Example 1, Figure 2 is an aberration curve diagram of Example 1, Figure 3 is a sectional view of Example 2, Figure 4 is an aberration curve diagram of Example 2, and Figure 5 is an aberration curve diagram of Example 2. A cross-sectional view of Example 3, and FIG. 6 is an aberration curve diagram of Example 3. G, ~G1...first to sixth group lenses, M...filler, T...projection tube surface glass. [Effects of the Invention] As explained above, according to the present invention, chromatic aberration is corrected,
It is possible to obtain a projection lens for projection TVs that has a large aperture ratio, a large angle of view, and has excellent imaging performance with a sufficient amount of peripheral light.

Claims (1)

[Claims] In order from the screen side, the first group lens is a positive lens, the second group lens is a meniscus-shaped positive lens, and the third group lens is a CR lens.
It consists of a negative lens with a more strongly concave surface facing the T side, the fourth group lens is a positive lens with convex surfaces on both sides, the fifth group lens is a positive meniscus lens, and the sixth group lens is a negative lens with a concave surface facing the screen side. , a projection lens for a projection television consisting of six elements, in which the second group lens and the sixth group lens are each plastic lenses having at least one aspherical surface, and the following conditions (a) to (e) are met. A projection lens for a projection television, which is characterized by satisfying the following. (a) 0.5<ψ_1_, _2<1.1 (b) 1.1<ψ_4_, _5<1.4 (c) 0.55<|ψ_3|<0.9, ν_3<40 (d) 0 .9<|ψ_6|<1.1 (e) 0<ψ_2<0.4 However, ψ_1_, _2: Combined power of the 1st group lens and 2nd group lens ψ_4_, _5: 4th group lens and 5th group lens Combined power of lens ψ_3: Power of 3rd group lens ψ_6: Power of 6th group lens ψ_2: Power of 2nd group lens (however, the power of the entire system is assumed to be 1) ν_3: Abbe number of 3rd group lens